Nanoparticles with high surface energy and chemical activity have drawn substantial attention in petroleum industry. Recently, Janus nanoparticles exhibited tremendous potential in enhanced oil recovery (EOR) due to their asymmetric structures and properties. In this study, a series of amphiphilic pseudo-Janus@OTAB (PJ@C18) nanoparticles with different concentrations of stearyltrimethylammoium bromide (OTAB) were successfully fabricated. The structures and properties of PJ@C18 were characterized by Fourier transform infrared spectroscopy and ζ-potential measurements. Based on the emulsification experimental results, the interaction models and the self-assembly behavior between hydrophilic nanoparticles (SiO 2 @NH 2 ) and OTAB molecules at the oil/water interface were proposed, which was further confirmed via the measurements of the contact angle and dynamic interfacial tension. Interestingly, it was found that the change of pH value from 7.5 to 4.0 caused the type reversal of the PJ@C18-1000 stabilized Pickering emulsions. Furthermore, the PJ@C18-1000 stabilized Pickering emulsion system with excellent salt and temperature tolerances (10000 mg·L −1 , 90 °C) significantly improved the oil recovery in the single-tube (more than 17%) and double-tube (more than 25%) sand pack model flooding tests. The findings of this study could help to better understand the construction mechanism of pseudo-Janus silica/surfactant assembly and the potential application of PJ@C18-1000 stabilized Pickering emulsions for EOR.
In recent years, silica nanoparticles (SNPs) attracted increasing attention in across various fields, especially in enhancing oil recovery (EOR). Herein, the thiol and dodecyl functionalized silica nanoparticles (fSNPs) grafted with different molar ratios of 3-mercaptopropyl trimethoxy-silane (KH590)/dodecyl trimethoxysilane (DTMS) (1:0, 1:0.2, 1:0.4, 1:0.8, 1:1.6 and 1:4.0) were successfully synthesized via a facile two-step method and subsequently employed to stabilize emulsions for EOR. The SNPs were characterized by the Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectrometer (EDS), thermogravimetric analysis (TGA) and transmission electron microscope (TEM). The water contact angle and interfacial tension (IFT) measurements confirmed the amphiphilicity of the fSNPs. Notably, the fSNPs (1:1.6) grafted with a moderate molar ratio of KH590/DTMS significantly decreased the IFT of n-octane/water interface from 51.0 mN/m to 15.0 mN/m. Both the optical microscopy and static multiple light scattering were utilized for systematical stability evaluation of the fSNPs-stabilized emulsions. The fSNPs (1:1.6) stabilized emulsion exhibited excellent stability and remarkable resifstance to temperature and salinity, which should be attributed to the rigid interfacial film generated by the amphiphilic fSNPs. Moreover, core-flooding experiments demonstrated that the fSNPs (1:1.6)-stabilized emulsion effectively plugged the pore throats and enhanced oil recovery by 18.63 %, confirming its excellent potential in EOR applications.
Yuan-li Li,Zhao Chen,Xiao-min Liu,Ling Wang,Zheng-gang Cui
The sulfobetaine and sulfonate surfactants derived from 1,3-dialkyl glyceryl ethers were examined as surfactants for enhanced oil recovery free of alkali in high salinity and high temperature reservoir conditions. The surfactants containing polyoxypropylene-polyoxyethylene chain are relatively hydrophilic and the sulfobetaines derived from symmetric and asymmetric 1,3-dialkyl glyceryl ethers are relatively hydrophobic. The binary mixtures at appropriate molar fraction ratio are well soluble in connate water with a total salinity as high as 20,000 mg/L including 800 mg/L Ca 2+ and 40 mg/L Mg 2+ , and can reduce the interfacial tension between the connate water and crude oil to 10 −3 ∼10 -4 mN/m magnitude at and beyond 60 °C in a wide total concentration range, 0.1∼5 mM. In addition, the formulations show good resistance to the adsorption by quartz sands and prefer to form crude oil-in-connate water (O/W) emulsions.
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